(1) Field of the Invention
This invention relates to novel quinazoline derivatives useful for the treatment of hypertension.
(2) Description of the Prior Art
Numerous quinazoline derivatives have been known to date, including especially piperazinoquinazolines such as various acid amide compounds, e.g., prazosin (Japanese Patent Publication No. 22135/1970; U.S. Pat. No. 3,511,836), terazosin (Japanese Patent Laid-Open No. 27588/1979; U.S. Pat. Nos. 4,026,894 and 4,112,097) and those disclosed in Japanese Patent Laid-Open No 116052/1982 as well as piperazinoquinazoline of the pyrimidine structure such as those disclosed in Japanese Patent Laid-Open No. 181068/1982 (U.S. Pat. Nos. 4,435,301, 4,483,857 and 4,483,859). These conventional quinazoline derivatives have been subjected to further investigations, whereby some of the quinazoline derivatives have already been clinically applied as antihypertensive agents. They are classified as .alpha.-adrenergic antihypertensive agents. Although they have excellent clinical effects, some drawbacks have been observed that they lack long-acting properties and develop orthostatic hypotension as an undesirable side effect.